Kinetic modeling and experimental validation of the autoclave process for the production of thermoplastic particle foams

• Applicants: Professor Dr.-Ing. Andreas Jess; Professor Dr.-Ing. Holger Ruckdäschel
• Subject Area: Plastics Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563668306

Thanks to their low densities, good insulation properties, unique mechanical properties and easy recyclability, thermoplastic particle foams make a significant contribution to sustainability, for example in thermal insulation in the construction industry, packaging, sole materials in sports shoes or energy absorbers in transportation. In addition to suspension polymerization and extrusion, the autoclave process is an important method for producing thermoplastic particle foams such as expanded polypropylene and expanded polyurethane. In this process, microgranulate is used as the starting material and processed into foamed granules in a stirred autoclave. First, a suspension is formed from the microgranulate in water and, if necessary, additives. One or more blowing agents, usually carbon dioxide or butane, are then applied at a specified pressure and temperature profile. The blowing agent should dissolve through diffusion processes, if possible until saturation. A rapid drop in pressure is then generated by expansion, which leads to segregation and foaming of the particles. Despite industrialized production, too little is known about the scientific and technical principles of foam particle production. This requires a better understanding of the heat and mass transfer processes, an exact determination of material variables and a model-based description of the process engineering processes. The planned project will make targeted use of the complementary expertise of the Chair of Polymer Engineering in the field of foam production and characterization and the Chair of Chemical Process Engineering in the field of sorption and mass transfer. The overall aim of the project is the kinetic modeling, experimental validation and data-based design of the autoclave process for the production of thermoplastic, semi-crystalline foam particles from PP. The project consists of several work packages from the analysis of the material data to the model-based description of the sorption behavior and autoclave tests to data-based modeling. First, specifically selected materials are processed into microgranulates and analytically characterized. From this, initial sorption models are established, which are validated using autoclave tests. In addition, the foams obtained are examined in order to build up an understanding along the process chain from raw material to particle foam. Finally, the results will be analyzed using machine learning methods in order to gain a deeper understanding of the process.

• DFG Programme: Research Grants